During a voice teleconference, it is often desirable for two or more conference participants to be able to both view and discuss common data objects such as a set of images. For example, one participant may desire to conduct a slide presentation concurrent with a voice conversation among the participants. Systems which enable a person to receive and view image data over a telephone line concurrent with voice conversation are known. One such system interrupts the telephone conversation momentarily to allow visual data to be transmitted over the telephone line. Following the transmission of visual data, the voice communication can be automatically resumed. Other known systems for sharing voice and image data generally require relatively complex equipment, specially enhanced modems, or dedicated high speed digital lines such as Internal Services Digital Network. Still other systems require multiple telephone lines to handle both data object manipulation and voice. Generally, the known desktop teleconferencing systems are for point-to-point communications rather than multipoint, multiparty communications.